The present invention broadly relates to the industry of construction and building materials and cement industry and, more specifically, to cements and processes for producing the same.
Cements containing alite, belite, celite are known. These cements find an extensive use in industry, though they have a low activity over the initial hardening period.
A process for the production of the above-mentioned cement is known which comprises grinding a raw mixture consisting of a calcareous and an acidic components, followed by grinding the resulting cement clinker. During the grinding stage, various additives may be introduced into the clinker, for example gypsum.
This known process for producing the above-mentioned cement has the disadvantage of requiring a high calcination temperature. The cement clinker produced by this process has a low millability thus causing high power consumption for its grinding.
A cement containing 5 to 60% by weight of calcium chloroaluminate and above 5% by weight of alite, belite and celite as well as additives of anhydrite and silicofluoride is also known.
The presence of calcium chloroaluminate in the cement imparts to the cement an increased activity at early stages of hardening. However, preparation of this cement is associated with the necessity of incorporation of additives of anhydrite and silicofluoride in order to prolong the setting time, since the cement without the above-mentioned additives has a very short setting time which restricts the fields of its application. Furthermore, incorporation of such retarding additives causes the decreased activity of the cement within the controlled period.
A process for the production of this cement containing alite, belite and celite as well as calcium chloroaluminate is also known, which comprises calcination of a raw mixture consisting of a calcareous, silicaceous or aluminous components, as well as a ferric component and calcium chloride at a temperature within the range of from 1,300.degree. to 1,400.degree. C, followed by grinding of the thus-produced cement clinker. At the grinding stage various additives in the form of sulphates, nitrates, chlorides of alkali or alkali-earth metals can be introduced into the clinker.
The prior art process for the production of the above-mentioned cement has the disadvantages that it is impossible to obtain chlorosilicate minerals (highly-basic calcium chlorosilicate, calcium chloro-orthosilicate) in the clinker and requires a high (1,300.degree. to 1,400.degree. C) temperature of the clinker-formation process which necessitates a high consumption rate of the fuel. Furthermore, the cement clinker produced by this process features an insufficient millability which also requires a high power consumption for grinding of the clinker.